Deny record target involving head of livestock (8)
I believe the answer is:
disclaim
'deny' is the definition.
(I know that disclaim is a kind of deny)
'record target involving head of livestock' is the wordplay.
'record' becomes 'disc' (eg a CD, compact disc).
'target' becomes 'aim' (both can mean a goal or purpose).
'involving' is an insertion indicator.
'head of' says to take the initial letters.
The first letter of 'livestock' is 'l'.
'disc'+'aim'='discaim'
'discaim' going around 'l' is 'DISCLAIM'.
(Other definitions for disclaim that I've seen before include "Deny or relinquish" , "Renounce" , "Forswear" , "Disown or deny, maybe responsibility" , "Deny, refuse to acknowledge" .)